<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    Object.prototype.a="a";
    var obj = {
        name:"达姆",
        age:18
    };

    console.log(Object.getOwnPropertyDescriptor(Object.prototype,"toString"))

   for(var item in obj){
       console.log(item)
   }



</script>
</html>